U.S. airlines are projected to notch a second consecutive year of 5% revenue growth in 2018, fueled by steady capacity additions, an uptick in passenger volume, improved yield and growth in demand for ancillaries. Despite a highly consolidated market – the top four airlines account for more than 80% of flown revenue – competition remains fierce among airlines and across distribution channels. This report provides complete sizing and analysis on the U.S. airline segment, including online and mobile bookings, distribution trends, OTA versus supplier dynamics, and projections through 2022.